2. Genetic expression is the process by which
inheritable information from a gene, such as
the DNA sequence, is made into a functional
gene product, such as protein or RNA
Non-protein coding genes (e.g. rRNA genes,
tRNA genes) are transcribed, but not
translated into protein
3. Group of organisms lacking a cell nucleus or any
other membrane-bound organelles.
Differ from the eukaryotes, which have a cell
nucleus
Mode of division is binary fission
Prokaryotes exhibit efficient genetic
mechanisms to respond to environmental
conditions
7. Inducible gene
− Regulated by inducer/activator
Constitutive gene
− Not subjected to regulation
8. Control at the level of transcription
Induction - the production of a specific
enzyme/s in response to the presence of a
substrate
Repression - the cessation of production of a
specific enzyme/s in response to an increased
level of a substrate
9. All of the genes which encode the enzymes
necessary for the pathway are found next to
each other on the E. coli chromosome
A single mRNA carries information for
multiple proteins
This type of mRNA is called a polycistronic
mRNA and is totally unique to prokaryotes
10. An operon model is a self-regulating series of
genes found on DNA that work in concert
It includes a special segment of genes that are
regulators of the protein synthesis, but do not
code for protein, called the promoter and
operator regions
Lactose (Lac), Tryptophan (Trp), L-Arabinose
(Ara)
11. Inducible system
Three genes part of an operon that code for
three separate enzymes
Needed for the breakdown of lactose, a
simple sugar
16. Lac I
Promoter
gene
Operator
gene
Lac Z Lac Y Lac A
mRNA
R R
RR
RNA polymerase
mRNA
Thiogalact
oside
transacetyl
ase
Permeas
e
β-
galactosidase Inducer
Inactive repressor
R
Lactose/
Isopropyl
Thiogalactosid
e (IPTG)
present
18. Lac I
Promoter
gene
Operator
gene
Lac Z Lac Y Lac A
cAMP ↑↑↑
Glucose pool gets depleted
due to metabolism
CAP-cAMP
complex formed
cAMP
RNA polymerase
mRNA
β-galactosidase
Permease
Thiogalactoside
transacetylase
If there occurs glucose metabolism
R
IR
I
23. 1. L-arabinose operon model
2. Controlled by a dual positive and
negative system
3. 3 structural genes: araB, araA, and
araD
4. Encode the metabolic enzymes for
breaking down arabinose for
further metabolism via the HMP
Shunt pathway